The recovery of europium in aqueous chloride solution by photochemical reduction/precipitation was evaluated in the presence of sulfate ions and a radical scavenger. A commercial low-pressure mercury lamp with an emission peak at 253.7 nm was used as an irradiation source. The influencing factors were investigated in detail with a pure europium (III) chloride solution and then applied to a solution containing a Gd/Eu molar ratio of 27. Europium recovery was shown to increase with an increase in SO42- /Eu molar ratio up to 7, which corresponds to a stoichiometric excess of 600%. Similarly, high scavenger requirements (formic acid/Eu ratio of 500) were needed to achieve high yields. Faster reaction rate in the presence of formic acid, as compared with 2-propanol (2 and 15 hr, respectively, at 99% Eu recovery), used as scavengers, was observed. This was related to the photo activation of formic acid, demonstrated by a strong absorption in the near-UV region, not observed with 2-propanol, and a ready drop of the solution Eh. Measurements of redox potential indicated the reducing character in the formic acid system. This reducing character, that was not observed with 2-propanol, increases with the irradiation at 253.7 nm. The increase in rare earth concentration led to either Eu(III) precipitation prior to irradiation, in pure Eu solutions, or Eu-Gd coprecipitation, in multicomponent solutions. Europium recovery reached 99% when the experiments were carried out with pure, dilute europium chloride solutions. High yields could not be achieved in the presence of high gadolinium concentration, owing to the Eu-Gd coprecipitation.